1. Field of the Invention
The present invention relates to a transmission apparatus using an in-band type SNMP (Simple Network Management Protocol) system.
2. Description of the Related Art
In a general transmission system, a group of apparatuses linked via transmission spans is located in a network forming the transmission system in a distributed formation. In such a real network configured by points (a group of apparatuses) and lines (a group of transmission lines), it is required to provide a management means or method for integrally managing the group of apparatuses and the group of transmission lines in such a manner that the network formed thereof is handled as only one object for management. Such a management means makes it possible to link the apparatuses arranged in the distributed formation and thus bring up the network to only one object.
In an STM (SONET/SDH) transmission system, the management means or method is realized by using an overhead provided separately from a user data field (payload) in a transmission frame. In the overhead, two independent data communication channels are defined. More particularly, the above two independent data communication channels are respectively a section DCC (192 kbps) and a line DCC (576 kbps) where DCC is an abbreviation of Data Communication Channel. A data packet having a control information field is transmitted via the data communication channels. In the control information field, headers in the respective hierarchical levels based on the information switch method in the OSI-7 layer are stacked. Thus, information concerning the apparatuses collected on the node basis is collected and delivered.
In an ATM (Asynchronous Transfer Mode) transmission system, a capability of transmitting data via the above-mentioned data communication channels is defined when loaded with the payload. More particularly, such a payload created in an STM(SONET/SDH) system (SONET: Synchronous Optical NETwork/Synchronous Digital Hierarchy) is used as a carrier. A fundamental operation/function in which a cell is placed in a logical transmission path/channel dynamically (or statically) set is monitored based on ATM switch information with which switch intelligence parts of the respective apparatuses are linked via meta channels.
However, the conventional ATM transmission system mentioned above is restricted to only a system having an operation/function in which cells are added and dropped as data on the transmission path/channel logically set on the payload carrier. In other words, the conventional ATM transmission system is designed without taking into account management of apparatus information on the data transmission side prior to cell assembly and that on the data transmission side after cell disassembly in a case where a CLAD (Cell Layer Assembly Disassembly) unit is provided in the transmission apparatus. The CLAD unit has the function of converting the data accommodation format of cells into another format, for example, the data accommodation format of a package and vice versa.
The LAN-system CLAD units provided in the ATM system which are linked together (as starting points of cell generation and ending points of cell termination) to transport cells by using the logical paths/channels set between the CLAD units view the above ATM system as a virtual facility for conveying packets.
Originally, a site manager is defined in the management system of the LAN facility. An SNMP (Simple Network Management Protocol) application is utilized in the site manager. Management information collection and delivery by SNMP packets that are created and terminated by the SNMP application is replaced by an ILMI (Integrated/Interim Local Management Interface) which is defined on the virtual facility via which the LAN-system CLAD units are linked.
The transparency of management information collection and delivery based on the SNMP process by means of the ILMI can provide a guarantee within a request management area of the site manager placed on the real LAN facility which is not the virtual facility. However, the above transparency can manage only resources placed on the LAN facility, such as LAN-system terminals and routers (a group of LAN nodes) That is, the transparency excludes the CLAD units as objects for management.
In order to correlate the site manager with the resource information of the CLAD units themselves that connote the ATM transmission, it is required to provide SNMP-based information understandable by the site manager from the apparatus equipped with the CLAD unit, irrespective of whether the ATM transmission is connoted.
Conventionally, each of the apparatuses equipped with the CLAD units respectively provides, via a system separate from the system involved in transmission of the SNMP information concerning the ATM transmission, the site manager with the SNMP information concerning data transmission. The above separate system is a dedicated or leased communication line. Thus, the CLAD units are added to the site manager as additional objects for management.
The use of the dedicated communication line for management of the CLAD units does not flexibly cope with a change of connections between the CLAD units.